The field of the invention is polyamide adhesives for textiles and the invention is particularly concerned with powdered mixtures of polyamides for heat sealing textiles by the powder dot process.
The state of the art of methods and apparatus for depositing powdered thermoplastic adhesive materials on the outer surface of textiles may be ascertained by reference to U.S. Pat. Nos. 4,139,613; 4,183,978; and 3,667,422; British Pat. No. 1,295,558, and the article entitled "From Basting to Binding Interlinings", in LICHTBOGEN 1972, no. 167 (5/XXI), pages 17-19, the disclosures of which are incorporated herein.
Copolyamides useful as adhesives and the state of the art thereof may be ascertained by reference to U.S. Pat. Nos. 2,252,555; 3,515,702; 3,839,121; 3,883,485; 3,883,487; 3,948,844; 3,950,297; 4,035,436; 4,046,747; 4,101,534 and U.S. Pat. No. Re. 27,939; British Pat. Nos. 1,458,640 and 1,548,431, Japanese Patent Application No. 76 19 034 as abstracted in Chemical Abstracts, Vol. 84 (1976) page 181,313g, and West German Published Applications Nos. 24 36 430 and 28 06 833, the disclosures of which are incorporated herein.
The state of the prior art of producing polyamide powders may be ascertained by reference to U.S. Pat. No. 4,143,025 and the Kirk-Othmer "Encyclopedia of Chemical Technology", 2nd ed., vol. 16 (1968) under the section "Polyamide (Plastics)", pages 88-105, particularly page 92--polylauryllactam (nylon-12), and polyundecamide (nylon-11), page 101, Solution Processes, and Powder Processing, pages 101-102, the disclosures of which are incorporated herein.
According to British Pat. No. 1,295,558, the spot coating of interlinings for textiles is carried out mainly by three methods:
1. A suitable plastic powder, for example, a polyamide or polyethylene based powder, is applied by a doctor blade to an engraving roller having recesses in the form of dots disposed in an even raster or grid formation and having a diameter of about 1 mm so that the plastic powder fills the recesses. The web of the interlining, which has been preheated to a high temperature by means of heating rollers, is passed around the engraving roller under tension and the plastic powder is transferred from the recesses to the web of interlining material (powder point or powder dot coating process).
2. A network of spots of a suitable plastic, such as polyethylene, is prepared in the form of a raster, the spots being interconnected by very fine webs. The network is applied dry to the hot interlining, the fine webs breaking up and disappearing, and the spots of the plastic fusing to the interlining. Interlinings of this kind have a relatively hard handle and can be fixed only on relatively heavy facing materials and the plastics also tend to bleed through and stick to the fixing press.
3. In the least expensive and least complex process, suitable plastics, such as PVC, polyamide or polyethylene, are mixed with plasticizers or in aqueous or solvent-containing media to form pastes which are printed by means of a printing roller formed with perforations arranged as a raster (paste printing process).
The condition for bonding textiles using the powder dot process are entirely different from the prior art uses of polyamide adhesives. By powder point process or powder dot coating process is meant the process especially described in U.S. Pat. No. 3,667,422 and as described as method one of British Pat. No. 1,295,558.
It is known to use copolyamides as thermoplastic adhesives for heat sealing textiles, in particular those containing the component lauryllactam, as disclosed in U.S. Pat. No. 3,515,702 and U.S. Pat. No. Re. 27,939. These thermoplastic adhesives evince good resistance to chemical cleaning in solvents, but on the other hand are not yet wholly satisfactory for the heat sealing of siliconized fabrics. Furthermore, they lack the "soft touch".
While copolyesters, especially polyether esters, evince a softer touch, they are less resistant to chemical cleaning.
Block copolymers are known from Japanese patent application No. 75 19034. These block copolymers are obtained from a polyamide-6-dicarboxylic acid, polytetrahydrofuran-diol and the transesterification of butanediol-(1,4) and dimethylterephthalate and dimethylisophthalate. Such copolyether ester amides evince too high a melting point and a low resistance to cleaning. The bonding shows excessive tendency to bleed through. Such products furthermore contain an excessive amount of extract.